chem chapter 3
experimental value
the value measure in the lab
cubic centimeter cm^3=1 mL; cube of sugar =1 cm^3
...
1 atom of gold
.000000000000000000000327 grams
kilometer (km)
1 km = 10^3; length of a bout 5 city blocks
3 temperature scales
1) celcius- based on the freezing point of water (0 degrees celcius) boiling point of water (100 degrees celcuis) conversion = degrees celcius = (degrees farenheit - 32) / 1.8
rules for sig figs in measurement
1) every non-zero digit in a measurement is significant i.e. 24.7 L, .31286 kg, 952 173 mm 2) zeroes between non-zero digits are significant i.e. 7003-4, 40.792-5 3) leftmost zeroes in front of a non zero digit are NOT significant (they are only place holders); when reading left to right, nothing is significant until the first non-zero digit i.e.-.00632-3 0.42-2 4) zeroes at the end of a number that are after a decimal point are significant i.e. 43.00-4 1.010- 4 5) zeroes at the rightmost end of a number but before an understood decimal are NOT significant i.e. 300 km - 1 70 000-1 275 410-5 6) there are 2 situations when numbers have an unlimited/infinite number of sig figs -1) counting numbers of items i.e. 24 crayons in a box, 16 people in the room -2) conversion factors i.e. 60 mins/1 hour=1 hour/60 mins
si temp
Kelvin
decimeter (dm)
10^1 dm=1 m; diameter of a large orange
centimeter (cm)
10^2=1 m; diameter of a shirt button
millimeter (mm)
10^3 mm=1m ; thickness of a dime
millilter mL
10^3mL=1L; 10 drops of water= 1 mL
microliter (mL)
10^6 ML=1 L; crystal of table salt = 1ML
macrometer (Mm)
10^6 Mm=1 m'diameter of a bacterial cell
nanometer (nm)
10^9 nm=1m thickness of RNA molecules
1 atom of gold
3.27 x 10^-23
1 gram of hydrogen (scientific notation)
6.02 x 10^23
1 gram of hydrogen
602000000000000000000000 atoms
sig figs
all of the digits known in a measurement plus one estimated digit
if converting a prefix to a prefix
always go through the base
si electric current
ampere
meter (m)
base unit; height of doorkob from the floor
LITER
base unit; quart of milk
Kelvins (K)
based on the concept of absolute zero (0 Kelvin, all molecular movement has stopped) conversion: K = degrees celcius +273 * note a change of 1 degree celcius is equivalent to a change of 1 K
farenheit scale
based on the freezing point of water (32 degrees f) and boiling point of water (212 degrees f) conversion: farenheit= 1.8 degrees celcius + 32
si luminous intensity
candela
energy
capacity to do work or produce heat, called a joule (J), common non-SI unit is calorie (cal) 1 cal is the quantity of heat that riases the temperature of one gram of pure water by 1 degrees celcius 1 Joule=.2390 cal 1 cal = 4.184 J
m temperature
celcius
accepted value
correct value for the measurements based on reliable references
division in scientific notation
divide the coeffecients and subtract the exponent in the denominator from the exponent in the numerator
equation for percent error
divide the error by the accepted value and multiply by 100
decimeter
equal to 10 cm, so 1L = 1 dm^3, 1000 mL = 1L and 1000 cm^3 = 1L so 1 mL=1 cm^3
equation to calculate error
error = experimental value-accepted value (EV-AV)
what are measurements fundamentalt to?
experimental science
addition and subtraction
exponents have to be the same
sig figs w/ multiplication and division
for calculators involving multiplication and divison the answer to the same number of sig figs as the measurement with the least number of sig figs
how does heat travel
from a warmer body of matter to a colder body of matter
positive powers of 10
go with base unit
negative power of 10
goes with prefix
m mass
gram
scientific notation
helps us write numbers faster and easier, has 2 parts- coefficient and power
accuracy
how close a measurement is to the actual or true value, to evaluate the accuracy of a measurement, it must be compared to the actual value
precision
how close a series of measurements are to each other, irrespective of the actual value, to evaluate precision of a measurement, you must compare the values of 2 or more of these repeated measurements
sig figs in calculators
in general a calculated answer cannot be more precise than the least precise measurement from which it was calculated i.e. a room was measured and reported to have the dimensions 7.7 meters (2 sig figs) by 5.4 meters (2 sf), calc area = 7.7m x 5.4m=41.6 m^2
negative integer
indicates number in standard form is <1
positive integer
indicates the number in standard from is >1
error
individual measurements can be accurate or inaccurate
what type of property is density
intensive
SI units
international system of units, a revised version of the metric system, 7 SI base units, 5 of which are most chommonly used by chemists (all other units can be derived from these), all measured quantities can be reported in SI units although sometimes it is more convenient or practical to use non-SI we use both, chemists treat Liter (L) as an SI even though its not, "unofficial
si mass
kilogram
see notes for metric prefixes and SI units
l.lsdjfoaids
volume m
liters
Mass
mass is not weight, weight is a force that measures the pull on a given mass by gravity (mass is the measure of the amount of matter), kilogram (kg) 1 kg=10^3 g; small textbook gram (g): metric base; dollar bill milligram (mg): 10^3 mg=1g; 10 grains of salt microgram (Mg) 10^6Mg= 1 g; particle of baking powder
m length
meter
si length
meter
si amount of substance
mole
liter
more convenient unit of volume and is equal to the amoundt of space by a cube that measure 1000 cm^3 = 1 L
multiplication in scientific notation
multiphy numbers in scientific notation, multiply the coefficients and add the exponents i.e. (3x10^4) x (2x10^2) = (3x2) x 10^4+2 = 6x10^6
power
multiply by 10 raised to a power where the power is an integer
coefficient
number between 1 and 10
measurements
quantities that include both a number and a unit, fundamental to experimental science, it is important to make measurements as well as decide they are correct and reasonable, encounter numbers that are very large or very small
si time
seconds
sig figs with addition and subtraction
should be rounded to the same number of decimal digits (NOT total digits) as the measurement with the least number of decimal digits ex. 31.5m+862.391m+100.26=994.151m=994.2, 9.942x10^2m
percent error
should be within .1 or 10% to be accurate, do not take the absolute value (this is different than the book)
metric system
simple and easy to use, based on multiples of 10, making it easy to convert between units
temperature scales
temperature is the measure of how hot or cold a body of matter is, heat only travels from a warmer body of matter to a colder body of matter, most substances expand when heated and contract when cooled, one important exception is water- water expands when it is freezes (so ice is less dense than liquid water which is why ice floats)
error
the difference between the experimental and accepted values
rounding
to round a number, one must first decide how many sig figs the answer should have; then look only at the digit to the right of the last sig fig, if the digit is <5, drop it and if the digit is > or = to 5, then you round up i.e. 87.073=87.1 m=8.71 x 10^1m
volume
v=lxwxh, SI unit is amount of space occupied by a cube that measures 1m^3
steps for converting between units its the metric system
we will use
steps for converting between units in the metric system
we will use FLM and no negative exponents during the problem (only at the end, if necessary, for the answer) 1) start with what you are given 2) if you are given a base unit or converting to a base unit the prpocess will be only one step, the power of 10 will go with the small unit or the lower one of the chart (see examples in good notes)
